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Ever Thought of Drinking Water as a Source of Iron?

By Julia Bird

When listing foods that are high in iron, a few spring to mind: liver, lean beef, green leafy vegetables, beans and lentils, fortified foods. Less well known yet rich sources include shellfish such as clams, molasses, soy flour and dried apricots. I am also keen to mention here that chocolate contains reasonable amounts of iron, with a 50 g quantity of dark chocolate containing 4 mg of iron, roughly the same amount as a beefy Big Mac. However, with iron requirements being rather high, especially for women aged 19-50 and pregnant women even more, adequate iron intakes depend not so much on the intake of a few high-iron foods, but rather the iron content of the entire diet. Other foods, such as bread and pasta, also contain reasonable levels of iron but their role in total iron supply is often overlooked in favor of the famous high-iron foods. For example, the consumption of iron-fortified breakfast cereals has made an important contribution to helping people in the US meet iron intake requirements over the past decades, according to data from the USDA.

But there are other sources of iron apart from foods in the diet. Dietary supplements make an important contribution to iron intakes in countries where their use is widespread (see Fulgoni, Keast, Bailey and Dwyer). Iron cooking pots improve the iron status of anemic individuals (Geerligs, Brabin and Omari), as does the addition of iron ingots into cooking pots (see a media story on Lucky Iron Fish). The water we drink also contains iron. The natural iron content of water varies considerably. While water that is high in iron is not considered to be a health hazard, treating water usually aims to keep levels below 0.3mg/l, as higher amounts will stain laundry and may have a metallic taste. Drinking water in the US provides about 5% of daily requirements for adult men, the elderly and older children, but less than 3% for women of childbearing age and pregnant women (World Health Organisation).

In countries where routine water treatment is not so common, such as in Bangladesh, the iron content of ground water can be much higher and become a more important source of iron. In fact, a fairly recent study found that the prevalence of iron deficiency was 0% in a population of rural women living in Bangladesh, most likely attributable to intakes of around 40 mg iron per day from drinking water (Merrill et al.).The effect of groundwater iron content was the focus of a recent publication from Rahman and colleagues. The authors mapped the iron content of groundwater in Bangladesh and related it to the iron status of a nationally representative sample of 16,000 non-pregnant, non-lactating women, preschool-aged and school-aged children. The iron content of the water was categorized into 10 categories that ranged from 0.18 mg/l and below, up to more than 10 mg/l, and mapped. A groundwater iron concentration >2.8 mg/l was considered to be “high”. Visually, around half the country has a “high” iron content in the groundwater used for drinking.

The authors found that the ground water iron concentration was a strong predictor of iron sufficiency. Even when considering that areas with a high iron content tended to occur in low socio-economic status areas, the results were robust and the relationship was maintained. Iron deficiency ranged from 5 – 10% in the three population groups studied and was not considered to be a major problem in the country. Any plans to improve the iron status of Bangladeshis through food-based interventions should take into account the underlying high iron intakes from groundwater.